Commit 213b3d1e authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: nv: Handle ERETA[AB] instructions 



Now that we have some emulation in place for ERETA[AB], we can
plug it into the exception handling machinery.

As for a bare ERET, an "easy" ERETAx instruction is processed as
a fixup, while something that requires a translation regime
transition or an exception delivery is left to the slow path.

Reviewed-by: default avatarJoey Gouly <joey.gouly@arm.com>
Reviewed-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240419102935.1935571-14-maz@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 6ccc971e

arch/arm64/kvm/emulate-nested.c

+20 −2
Original line number Diff line number Diff line
@@ -2172,7 +2172,7 @@ static u64 kvm_check_illegal_exception_return(struct kvm_vcpu *vcpu, u64 spsr) 


void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)

{

	u64 spsr, elr;

	u64 spsr, elr, esr;



	/*

	 * Forward this trap to the virtual EL2 if the virtual
@@ -2181,11 +2181,29 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu) 
	if (forward_traps(vcpu, HCR_NV))

		return;



	/* Check for an ERETAx */

	esr = kvm_vcpu_get_esr(vcpu);

	if (esr_iss_is_eretax(esr) && !kvm_auth_eretax(vcpu, &elr)) {

		/*

		 * Oh no, ERETAx failed to authenticate.  If we have

		 * FPACCOMBINE, deliver an exception right away.  If we

		 * don't, then let the mangled ELR value trickle down the

		 * ERET handling, and the guest will have a little surprise.

		 */

		if (kvm_has_pauth(vcpu->kvm, FPACCOMBINE)) {

			esr &= ESR_ELx_ERET_ISS_ERETA;

			esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC);

			kvm_inject_nested_sync(vcpu, esr);

			return;

		}

	}



	preempt_disable();

	kvm_arch_vcpu_put(vcpu);



	spsr = __vcpu_sys_reg(vcpu, SPSR_EL2);

	spsr = kvm_check_illegal_exception_return(vcpu, spsr);

	if (!esr_iss_is_eretax(esr))

		elr = __vcpu_sys_reg(vcpu, ELR_EL2);



	trace_kvm_nested_eret(vcpu, elr, spsr);

arch/arm64/kvm/handle_exit.c

+2 −1
Original line number Diff line number Diff line
@@ -248,7 +248,8 @@ static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu) 


static int kvm_handle_eret(struct kvm_vcpu *vcpu)

{

	if (esr_iss_is_eretax(kvm_vcpu_get_esr(vcpu)))

	if (esr_iss_is_eretax(kvm_vcpu_get_esr(vcpu)) &&

	    !vcpu_has_ptrauth(vcpu))

		return kvm_handle_ptrauth(vcpu);



	/*

arch/arm64/kvm/hyp/vhe/switch.c

+11 −2
Original line number Diff line number Diff line
@@ -208,7 +208,8 @@ void kvm_vcpu_put_vhe(struct kvm_vcpu *vcpu) 


static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code)

{

	u64 spsr, mode;

	u64 esr = kvm_vcpu_get_esr(vcpu);

	u64 spsr, elr, mode;



	/*

	 * Going through the whole put/load motions is a waste of time
@@ -242,10 +243,18 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code) 
		return false;

	}



	/* If ERETAx fails, take the slow path */

	if (esr_iss_is_eretax(esr)) {

		if (!(vcpu_has_ptrauth(vcpu) && kvm_auth_eretax(vcpu, &elr)))

			return false;

	} else {

		elr = read_sysreg_el1(SYS_ELR);

	}



	spsr = (spsr & ~(PSR_MODE_MASK | PSR_MODE32_BIT)) | mode;



	write_sysreg_el2(spsr, SYS_SPSR);

	write_sysreg_el2(read_sysreg_el1(SYS_ELR), SYS_ELR);

	write_sysreg_el2(elr, SYS_ELR);



	return true;

}